The present invention relates to a spherical ball used for a tip portion of a ball-point pen and relates to a ball-point pen utilizing the ball.
Conventionally, in a tip portion of a ball-point pen, a ball for a ball-point pen is rotatably held by an edge portion which is formed by crimping the tip end portion inwards and by the ball seat portion of the tip main body. One part of the ball protrudes outside from the edge portion and the ball rotates in a ball-holding chamber formed by the edge portion and the ball seat portion to supply ink to the tip portion. As a ball for the ball-point pen, high abrasion resistance is required to the material for the ball and therefore super steel material is generally used.
As described above, the ball for a ball-point pen held in the ball-holding chamber supplies ink by rotating while the ball is contacting with the edge portion and the ball seat portion. Thus the ball is necessary to have enough abrasion resistance with respect to the edge portion and the ball seat portion. However, when the abrasion resistance of the ball is inadequate, abrasion easily occurs due to the contacting rotation of the ball with the edge portion and the ball seat portion and a smooth rotation is not attained frequently. As a result, a blur of a line occurs and the thickness of the ink is liable to change when the ball-point pen is used. This leads to a problem of reduction in writing performance. Therefore, conventionally in general, the super steel material whose hardness is extremely high is used as a ball for a ball-point pen. However, as the super steel material has a very high hardness in itself, its processing of the ball is very difficult, which leads to high in manufacturing cost and hours.
Also, a ball-point pen is required to have smoothness and consistent operation when the ball-point pen is used. Thus a lubricating ability is required of the ball in itself. However, for increasing the lubricating ability on the surface of the ball which is made of super steel material, it is necessary to improve the surface smoothness and the sphericity of the ball by grinding for a long working time, which results in more increasing manufacturing cost and time.
The object of the present invention is to provide a ball for a ball-point pen and a ball-point pen with the use of it, which are superior in easy manufacture and possesses a good abrasion resistance and a good lubricating ability. Disclosure of invention
In accordance with a ball for a ball-point pen as set forth in claim 1 of the present invention, stainless steel is used for the material and the surface of the material is formed with a nitrosulphurized layer. According to the present invention, the spherical shape of the ball is easily attained, and the ball for a ball-point pen can be obtained which is superior in abrasion resistance and lubricating ability by utilizing the nitrosulphurized layer.
In accordance with a ball for a ball-point pen as set forth in claim 2, the nitrosulphurized layer has an iron nitride layer and an iron sulphide layer by means of reacting the iron on the surface of the stainless steel with nitrogen and sulfur. Thus, the iron nitride layer makes the ball attain abrasion resistance which is approximately equal to that of a super steel material, and the iron sulphide layer makes the ball have lubricating ability which is extremely satisfactory.
In accordance with a ball for a ball-point pen as set forth in claim 3, aluminum chrome molybdenum steel is used for the material and the surface of the material is formed with a nitrosulphurized layer. Therefore, the ball shape can be easily obtained and a ball for a ball-point pen can be obtained which is superior in abrasion resistance and lubricating ability due to the nitrosulphurized layer.
In accordance with a ball for a ball-point pen as set forth in claim 4, the nitrosulphurized layer has an iron nitride layer and an iron sulphide layer by means of reacting the iron on the surface of the aluminum chrome molybdenum steel with nitrogen and sulfur. Thus, the iron nitride layer makes the ball attain abrasion resistance which is approximately equal to that of super steel material, and the iron sulphide layer makes the ball have lubricating ability which is extremely satisfactory.
In accordance with a ball for a ball-point pen as set forth in claim 5, the aluminum chrome molybdenum steel is SACM 645 which contains chrome of 1.3-1.7%. The SACM 645 is easy to process into a spherical shape because its workability is superior before the nitrosulphurizing process is conducted, and after the nitrosulphurizing process, its hardness increases markedly to make the steel material superior in abrasion resistance and lubricating ability. The processing gives the ball superior quality for use as a ball for a ball-point pen.
In addition, in accordance with a ball-point pen utilizing such a ball as described in each of the claims above, writing performance is extremely satisfactory along with its durability.